A fungal strain isolated from stored wheat straw and identified as Aspergillus flavipes was found to produce an extracellular endo-1,4,beta-D-xylanase when grown in shake-culture of a mineral salt medium containing 0.1% wheat strawxylan as a sole source of carbon for 3 days at 28 degrees C. The enzyme was separated by precipitation with ammonium sulphate and desalted by Sephadex G-25 column. Fractionation and purification of the enzyme were carried out by chromatography on Bio-Gel P-100. The purified enzyme (mol wt 45,000) was found to release xylooligomers only from beta-1,4-xylan. It showed maximum activity at pH 5.0 and temperature 55 degrees C.